United States Army personnel and dependents who have tested seropositive for the Human Immunodeficiency Virus (HIV) are given medical examinations and treatment at Walter Reed Army Medical Center. Subjects are also invited to participate in a research protocol to study the natural history of HIV infection, conducted by the Walter Reed Army Institute of Research. An oral health research component conducted by NIDR is a part of this natural history study. The oral component documents the prevalence and incidence of oral pathologic conditions in relation to the stage of HIV infection and systemic disease. Risk factors associated with these conditions are also characterized, and the role of oral manifestations as early predictors or markers of disease progression are studied. Areas of emphasis are mucosal pathologies, periodontal conditions, candidal infections, and salivary constituents. Results to date show an increase in mucosal pathology as T4 cell counts decrease with progression of HIV disease. The most commonly observed mucosal pathologies were oral candidiasis and hairy leukoplakia. Destructive periodontal disease has occurred in about 25 percent of subjects examined. Longitudinal studies showed that about 30% of persons free from mucosal pathology at entry presented with pathology after six months of follow-up.